1. Field of the Invention
The present invention relates to a naphthalene compound and a light-emitting device using the compound.
2. Description of the Related Art
Recent progress of an organic light-emitting device is remarkable, and the characteristics of the device enable a thin and light weight light-emitting device with a high luminance at a low applied voltage, a variety of emission wavelengths, and a high-speed responsibility. From this fact, it is suggested that the device have potential to find use in a wide variety of applications.
However, in the present circumstances, an optical output with a higher luminance or a higher conversion efficiency is needed. In addition, the organic light-emitting device still involves a large number of problems in terms of durability such as a change over time due to long-term use and degradation due to an atmospheric gas containing oxygen, moisture or the like. Further, when the application of the device to a full-color display or the like is taken into consideration, the emission of blue, green, or red light with good color purity is needed. However, these problems have not been sufficiently solved yet.
In addition, a large number of aromatic compounds and fused ring aromatic compounds have been researched because of the potential of each of the compounds to serve as a fluorescent organic compound to be used in, for example, an electron-transporting layer or a light-emitting layer. However, it is hard to say that a compound capable of sufficiently satisfying emission luminance and durability has been obtained.
The case where any such aromatic compound or fused ring aromatic compound is used as a component for an organic light-emitting device is described in, for example, each of Japanese Patent Applications Laid-Open No. 2004-281390, No. 2006-045503, No. 2004-139957, No. 2004-204238, and International Publication No. WO2004/078872. Each of Japanese Patent Applications Laid-Open No. 2004-281390, No. 2006-045503, No. 2004-139957, and No. 2004-204238 discloses, as a component for an organic light-emitting device, a compound containing a naphthalene skeleton having a fused ring aromatic group at each of the 2- and 7-positions thereof. Japanese Patent Application Laid-Open No. 2004-281390 discloses the application of a material having a tricyclic fused heterocyclic group to an organic light-emitting device. Japanese Patent Application Laid-Open No. 2006-045503 discloses the application of a material containing a naphthalene skeleton having a substituent at each of the 2- and 7-positions thereof as a core to an organic light-emitting device. In addition, each of Japanese Patent Applications Laid-Open No. 2004-139957 and No. 2004-204238, and International Publication No. WO2004/078872 discloses the application of a compound having two fused tetracyclic aromatic hydrocarbon groups at the 1- and 5-positions or 2- and 6-positions thereof on a naphthalene ring to an organic light-emitting device.
In order to apply an organic light-emitting device to a display apparatus such as a display, it is necessary to secure an optical output with a high efficiency and a high luminance, and, at the same time, to secure high durability sufficiently. However, it cannot be said that the technologies described in any one of Japanese Patent Applications Laid-Open No. 2004-281390, No. 2006-045503, No. 2004-139957, and No. 2004-204238, and International Publication No. WO2004/078872 can sufficiently solve those problems.